Hercules Base Hit II V Hercules Bolier Fluid

I have a hydronic system which has a slight leak under the WEIL-McLAIN GOLD GV Series 4 boiler (contains Cryo-tec), has anyone got any ideas to a common place for the leak on this particular model (I have not removed any insulation for a closer look as of yet), and also if not possible to repair what repair solution should I add to the system........Hercules Base Hit II or Hercules Bolier Fluid........I was just trying to understand the difference between the two.